Treatment method of high-concentration unsymmetrical dimethylhydrazine wastewater

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a high-concentration unsymmetrical dimethylhydrazine wastewater treatment method which comprises the following steps: A) performing filtration pretreatment on unsymmetrical dimethylhydrazine wastewater; b) directly performing electron beam circulating irradiation treatment on the filtered wastewater, and accumulating the electron beam absorbed dose without adding chemical agents; c) detecting unsymmetrical dimethylhydrazine concentration and COD (Chemical Oxygen Demand) concentration of the wastewater subjected to electron beam irradiation treatment; when the removal rate of unsymmetrical dimethylhydrazine in the wastewater is greater than or equal to 90% and the removal rate of COD (Chemical Oxygen Demand) is greater than or equal to 80%, the wastewater enters an electrochemical reactor to be subjected to electrochemical reaction; d) detecting unsymmetrical dimethylhydrazine concentration and COD (Chemical Oxygen Demand) concentration of the wastewater after the electrochemical reaction; and when the concentration of unsymmetrical dimethylhydrazine in the wastewater is less than 0.5 mg / L and the COD is less than 120mg / L, entering the next step of treatment when the treatment requirement is met. According to the method, the degradation rate of unsymmetrical dimethylhydrazine and the COD removal rate can be effectively improved, and harmless treatment of the wastewater can be realized by adopting simple operation steps.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for treating high-concentration unsymmetrical dimethylhydrazine wastewater. Background Art

[0002] In recent years, my country's aerospace industry and military industry have been booming, and liquid propellants, as an important part of the aerospace industry and military industry, have played an indispensable role. Liquid propellants have the advantages of high specific impulse, easy thrust adjustment, multiple ignitions, and pulse operation. They dominate large-scale space transportation systems and various auxiliary propellant systems, and are widely used in various tactical and strategic missile terminal repair systems, large rockets, and attitude and orbit control systems of various spacecraft.

[0003] Liquid propellants used at room temperature mainly include combustion agents (undimethylhydrazine, methylhydrazine) and oxidants (nitrogen tetroxide, red fuming nitric acid). Unsymmetrical dimethylhydrazine is 1,1-dimethylhydrazine, with a molecular formula of C2H8N2 and a combustion heat of 3.3×10 7 J / kg. Liquid propellants also have high biological toxicity. For example, UDMH is included in both the "Catalogue of Highly Toxic Chemicals" and the "List of Highly Toxic Articles". It has high carcinogenicity (95.6%), mutagenicity (76.2%), teratogenicity (68.9%) and embryotoxicity (67.2%). It is also volatile. Once it enters the ecosystem, the consequences will be disastrous. Therefore, it must be rendered harmless.

[0004] At present, the main methods for treating UDMH wastewater are physical, biological and chemical methods. Physical methods include incineration, ion exchange and activated carbon adsorption. The incineration method consumes a lot of energy and has a high investment cost; the materials of the ion exchange method are expensive, and the analytical solution is difficult to handle, and there are problems such as secondary pollution; the activated carbon adsorption method only adsorbs and transfers pollutants such as UDMH, and does not achieve true degradation treatment, so there is secondary pollution of materials. At the same time, the treatment capacity and effect are greatly affected by the quality of the wastewater. Therefore, the application of activated carbon adsorption and ion exchange methods in the treatment of UDMH is limited.

[0005] The chemical oxidation method is to treat UDMH by using oxidants such as ozone, sodium hypochlorite, hydrogen peroxide, or ultraviolet catalytic oxidation, Fenton oxidation, electrocatalytic oxidation, etc. The chemical method has low treatment efficiency and the problem of secondary pollution caused by the addition of reagents or catalysts.

[0006] The biological method has the characteristics of low operating cost, easy operation and large processing capacity. However, when treating UDMH wastewater, due to the toxicity and difficulty in degradation of UDMH wastewater, the biochemical system's processing capacity is seriously inhibited, making it difficult to apply to the treatment of high-concentration UDMH wastewater. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a method for treating high-concentration dimethylhydrazine wastewater, which can effectively improve the degradation rate of dimethylhydrazine and the COD removal rate, and achieve harmless treatment of wastewater using simple operating steps.

[0008] The present invention provides a method for treating high-concentration unsymmetrical dimethylhydrazine wastewater, comprising the following steps:

[0009] A) filtering and pre-treating the unsymmetrical dimethylhydrazine wastewater;

[0010] B) directly subjecting the filtered wastewater to electron beam cyclic irradiation treatment to accumulate absorbed dose without adding chemical agents;

[0011] C) detecting the concentration of UDMH and COD in the wastewater after the electron beam irradiation treatment, and calculating the removal rate; when the removal rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%, the wastewater enters the electrochemical reactor to perform an electrochemical reaction; during the electrochemical reaction, an electrolyte is added to ensure the reaction efficiency;

[0012] When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is irradiated with a circulating electron beam until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%.

[0013] D) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and the COD is less than 120 mg / L, the wastewater is discharged; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and the COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

[0014] Preferably, in step A), in the UDMH wastewater, the concentration of UDMH is 10,000-50,000 mg / L, and the COD concentration is 20,000-100,000 mg / L.

[0015] Preferably, in step B), the absorbed dose of a single electron beam irradiation is 10 to 50 kGy.

[0016] Preferably, in step B), the filtered wastewater is directly subjected to electron beam irradiation treatment under the action of electrocatalysis to accumulate absorbed dose without adding chemical agents.

[0017] Preferably, the current density of the electrocatalysis is 800-1500 mA / cm 2 The electrocatalytic residence time is 2 to 12 hours.

[0018] Preferably, in step B), the parameters of the electron beam irradiation treatment include:

[0019] The electron accelerator energy is 0.5-10.0 MeV, the beam current is 2-80 mA, the single irradiation dose is 10-50 kGy, and the water film thickness under the beam is 0.05-1.0 cm.

[0020] Preferably, in step C), the electrolyte comprises NaCl or Na2SO4.

[0021] Preferably, in step C), electrolytes are added during the electrochemical reaction to ensure that the TDS concentration in the water is above 5000 mg / L.

[0022] Preferably, in step C), the temperature of the electrochemical reaction does not exceed 40°C.

[0023] The invention provides a method for treating high-concentration unsymmetrical dimethyl hydrazine wastewater, comprising the following steps: A) filtering the unsymmetrical dimethyl hydrazine wastewater for pretreatment; B) directly subjecting the filtered wastewater to electron beam cyclic irradiation treatment to absorbance accumulation without adding chemical agents; C) detecting the unsymmetrical dimethyl hydrazine concentration and COD concentration in the wastewater after the electron beam irradiation treatment to calculate the removal rate; when the unsymmetrical dimethyl hydrazine removal rate in the wastewater is ≥90% and the COD removal rate is ≥80%, the wastewater enters an electrochemical reactor to perform an electrochemical reaction; and during the electrochemical reaction, an electrolyte is added to ensure the reaction efficiency. rate; when the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is subjected to cyclic electron beam irradiation treatment until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%; D) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and COD is less than 120 mg / L, the wastewater is discharged; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment. In the present invention, the filtered wastewater is directly subjected to electron beam irradiation treatment, and the dose accumulation is performed without adding any chemical agent; then, the degradation rate of unsymmetrical dimethyl hydrazine and the COD removal rate of the wastewater after the electron beam irradiation treatment are detected; when the degradation rate of unsymmetrical dimethyl hydrazine in the wastewater is ≥90% and the COD removal rate is ≥80%, it enters the electrochemical reactor to carry out an electrochemical reaction; when the set value is not reached, it enters the irradiation water inlet pool and continues the cyclic electron beam irradiation treatment. Further, electrocatalysis can cooperate well with electron beam irradiation to effectively improve the degradation rate and COD removal rate of unsymmetrical dimethyl hydrazine. The present invention can effectively improve the degradation rate and COD removal rate of unsymmetrical dimethyl hydrazine, and the harmless treatment of wastewater can be achieved by using simple operating steps. At the same time, the treatment method provided by the present invention is simple, efficient, economical and environmentally friendly. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a method for treating high-concentration unsymmetrical dimethylhydrazine wastewater, comprising the following steps:

[0026] A) filtering and pre-treating the unsymmetrical dimethylhydrazine wastewater;

[0027] B) directly subjecting the filtered wastewater to electron beam cyclic irradiation treatment to accumulate absorbed dose without adding chemical agents;

[0028] C) detecting the concentration of UDMH and COD in the wastewater after the electron beam irradiation treatment, and calculating the removal rate; when the UDMH removal rate (UDMH degradation rate) in the wastewater is ≥90% and the COD removal rate is ≥80%, entering the electrochemical reactor to perform an electrochemical reaction; during the electrochemical reaction, an electrolyte is added to ensure the reaction efficiency;

[0029] When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is subjected to electron beam cyclic irradiation treatment until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%;

[0030] D) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and the COD is less than 120 mg / L, the wastewater is discharged from the treatment system; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and the COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

[0031] In step A):

[0032] The unsymmetrical dimethylhydrazine wastewater is filtered and pre-treated.

[0033] In certain embodiments of the present invention, in the UDMH wastewater, the concentration of UDMH is 10,000-50,000 mg / L, and the COD concentration is 20,000-100,000 mg / L.

[0034] Filtering the unsymmetrical dimethylhydrazine wastewater can remove large suspended particles in the wastewater and avoid clogging of pipes and electron accelerator reactors.

[0035] In step B):

[0036] The filtered wastewater is directly subjected to electron beam cyclic irradiation treatment to accumulate absorbed doses without adding chemical agents.

[0037] In the present invention, the filtered wastewater does not need to be added with any chemical agent (such as oxidant, synergist, etc.), and can be directly subjected to electron beam irradiation treatment to perform dose accumulation.

[0038] In some embodiments of the present invention, the absorbed dose of a single electron beam irradiation is 10-50 kGy.

[0039] In certain embodiments of the present invention, the filtered wastewater is directly subjected to electron beam irradiation treatment under the action of electrocatalysis to perform dose accumulation without adding chemical agents.

[0040] The current density of the electrocatalysis is 800-1500 mA / cm 2 The electrocatalytic residence time is 2 to 12 hours.

[0041] In some embodiments of the present invention, the parameters of the electron beam irradiation treatment include:

[0042] The electron accelerator energy is 0.5-10.0 MeV, the beam current is 2-80 mA, the single irradiation dose is 10-50 kGy, and the water film thickness under the beam is 0.05-1.0 cm.

[0043] The mechanism of electron beam irradiation includes the direct radiation of high-energy electron beams, and the excitation of water molecules by electron beams to produce hydroxyl radicals (·OH), hydrated electrons (e aq - ), the oxidation-reduction reaction of active particles such as hydrogen atoms (H·), and H2O2, as shown in formula (1).

[0044]

[0045] In formula (1), the value in brackets is the yield of the corresponding particles (G value), which represents the number of particles of this type generated for every 100 eV of energy absorbed.

[0046] In the present invention, electrocatalysis can cooperate well with electron beam irradiation. After electron beam irradiation, UDMH is effectively degraded, and the intermediate product and the increased ion concentration are more conducive to the electrochemical method. Therefore, the two can play a good synergistic role and effectively improve the degradation rate of UDMH and the COD removal rate.

[0047] In certain embodiments of the present invention, the electron beam irradiation treatment is carried out in an irradiation reactor. Wastewater passes through the irradiation reactor to form a water film, and the water flows through the electron beam lower scanning window to complete the irradiation process.

[0048] In step C):

[0049] Detecting the concentration of UDMH and COD in the wastewater after the electron beam irradiation treatment and calculating the removal rate; when the removal rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%, the wastewater enters the electrochemical reactor to perform an electrochemical reaction; during the electrochemical reaction, an electrolyte is added to ensure the reaction efficiency;

[0050] When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is subjected to cyclic electron beam irradiation treatment until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%.

[0051] In certain embodiments of the present invention, the electrolyte includes NaCl or Na2SO4; the electrolyte is added during the electrochemical reaction to ensure that the TDS concentration in the water is above 5000 mg / L.

[0052] In some embodiments of the present invention, the temperature of the electrochemical reaction does not exceed 40°C, such as 35°C.

[0053] In some embodiments of the present invention, the cyclic electron beam irradiation treatment is performed under the action of electrocatalysis. The parameters of the cyclic electron beam irradiation treatment are the same as the parameters of the above-mentioned electron beam irradiation treatment.

[0054] Specifically, the parameters of the cyclic electron beam irradiation treatment include:

[0055] The electron accelerator energy is 0.5-10.0 MeV, the beam current is 2-80 mA, the single irradiation dose is 10-50 kGy, and the water film thickness under the beam is 0.05-1.0 cm.

[0056] In certain embodiments of the present invention, wastewater after electron beam irradiation that meets set standards enters an electrochemical reactor for electrochemical reaction; wastewater that does not meet the standards enters an irradiation water inlet pool for continued cyclic electron beam irradiation treatment.

[0057] In step D):

[0058] The concentration of UDMH and COD in the wastewater after the electrochemical reaction is detected; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and COD is less than 120 mg / L, the wastewater is discharged from the treatment system; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

[0059] The treatment method provided by the present invention can reduce the types of reagents and the amount of reagents used, does not generate sludge and hazardous waste, reduces operating costs, and avoids secondary pollution;

[0060] The present invention can shorten the process chain and adapt to project site applications;

[0061] The present invention can flexibly adjust the number of cycles of the electron beam reaction to adapt to the harmless treatment and disposal of unsymmetrical dimethylhydrazine wastewater with different initial concentrations;

[0062] The present invention can solve the problems of poor treatment effect, secondary pollution, long treatment time, etc. of high-concentration unsymmetrical dimethylhydrazine.

[0063] The present invention can meet the situation of discontinuous on-site startup and unconfirmed water supply time, and the process startup time is short.

[0064] The present invention has no particular limitation on the sources of the reagents used above, and they can be commercially available.

[0065] In order to further illustrate the present invention, a method for treating high-concentration unsymmetrical dimethylhydrazine wastewater provided by the present invention is described in detail below in combination with embodiments, but it should not be understood as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] In the UDMH wastewater, the volume concentration of UDMH is 5% (40300 mg / L) and the COD concentration is 72000 mg / L;

[0068] 1) Filter the unsymmetrical dimethylhydrazine wastewater to remove large suspended solids in the wastewater, and then enter the electron beam inlet pool;

[0069] 2) The wastewater in the electron beam inlet pool is lifted by a water pump and enters the irradiation reactor for direct electron beam irradiation treatment to accumulate the dose without adding chemical agents;

[0070] The parameters of the electron beam irradiation treatment include:

[0071] The electron accelerator energy is 10MeV, the beam current is 10mA, the single irradiation dose is 20kGy, and the water film thickness under the beam is 1.0cm;

[0072] 3) The wastewater after the electron beam irradiation treatment is collected into an electron beam outlet pool; the degradation rate of UDMH and the COD removal rate in the wastewater after the electron beam irradiation treatment are detected; when the degradation rate of UDMH in the wastewater is ≥90% and the COD removal rate is ≥80%, the wastewater enters an electrochemical reactor and undergoes an electrochemical reaction at 35° C.; during the electrochemical reaction, an electrolyte (NaCl) is added to ensure that the TDS concentration in the water is above 5000 mg / L;

[0073] When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is irradiated with a circulating electron beam until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%.

[0074] The parameters of the cyclic electron beam irradiation treatment include:

[0075] The electron accelerator energy is 10MeV, the beam current is 10mA, the single irradiation dose is 20kGy, and the water film thickness under the beam is 1.0cm;

[0076] 4) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and COD is less than 120 mg / L, the wastewater is discharged from the treatment system; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

[0077] The relevant parameters and effect data of the treatment process of unsymmetrical dimethylhydrazine wastewater in Example 1 are shown in Table 1.

[0078] Table 1 Related parameters and effect data of UDMH wastewater during treatment in Example 1

[0079]

[0080]

[0081] Example 2

[0082] In the UDMH wastewater, the volume concentration of UDMH is 1.25% (10079.35 mg / L) and the COD concentration is 17600 mg / L;

[0083] 1) Filter the unsymmetrical dimethylhydrazine wastewater to remove large suspended solids in the wastewater, and then enter the electron beam inlet pool;

[0084] 2) The wastewater in the electron beam inlet pool is lifted by a water pump and enters the irradiation reactor, where it is directly irradiated by the electron beam under the action of electrocatalysis;

[0085] The electrocatalytic current density is 1000 mA / cm 2 ;

[0086] The parameters of the electron beam irradiation treatment include:

[0087] The electron accelerator energy is 1.5MeV, the beam current is 50mA, the single irradiation dose is 10kGy, and the water film thickness under the beam is 0.5cm;

[0088] 3) The wastewater after the electron beam irradiation treatment is collected into an electron beam outlet pool; the degradation rate of UDMH and the COD removal rate of the wastewater after the electron beam irradiation treatment are detected; when the degradation rate of UDMH in the wastewater is ≥90% and the COD removal rate is ≥80%, the wastewater enters an electrochemical reactor and undergoes an electrochemical reaction at 35° C.; during the electrochemical reaction, an electrolyte (NaCl) is added to ensure that the TDS concentration in the water is above 5000 mg / L;

[0089] When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is irradiated with a circulating electron beam until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%.

[0090] The parameters of the cyclic electron beam irradiation treatment include:

[0091] The electron accelerator energy is 1.5MeV, the beam current is 50mA, the single irradiation dose is 10kGy, and the water film thickness under the beam is 0.5cm;

[0092] 4) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and COD is less than 120 mg / L, the wastewater is discharged from the treatment system; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

[0093] The relevant parameters and effect data of the treatment process of unsymmetrical dimethylhydrazine wastewater in Example 2 are shown in Table 2.

[0094] Table 2 Related parameters and effect data of UDMH wastewater during treatment in Example 2

[0095]

[0096] The experimental results show that the content of UDMH in the wastewater treated by the method provided by the present invention meets the standard specified in GJB 3485A-2011, thereby reducing its harm to the environment and human body.

[0097] By comparing Example 1 and Example 2, it can be seen that the treatment can also meet the standards by using irradiation technology alone, but the required absorbed dose is high and the equipment processing capacity is low, resulting in high operating expenses and investment costs.

[0098] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating high-concentration unsymmetrical dimethylhydrazine wastewater, comprising the following steps: A) filtering and pre-treating the unsymmetrical dimethylhydrazine wastewater; B) directly subjecting the filtered wastewater to electron beam cyclic irradiation treatment to accumulate absorbed dose without adding chemical agents; C) detecting the concentration of UDMH and COD in the wastewater after the electron beam irradiation treatment, and calculating the removal rate; when the removal rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%, the wastewater enters the electrochemical reactor to perform an electrochemical reaction; during the electrochemical reaction, an electrolyte is added to ensure the reaction efficiency; When the removal rate of UDMH is less than 90% and / or the removal rate of COD is less than 80%, the wastewater enters the irradiation water inlet pool and is irradiated with a circulating electron beam until the degradation rate of UDMH in the wastewater is ≥90% and the removal rate of COD is ≥80%. D) detecting the concentration of UDMH and COD in the wastewater after the electrochemical reaction; when the concentration of UDMH in the wastewater is less than 0.5 mg / L and the COD is less than 120 mg / L, the wastewater is discharged; when the concentration of UDMH in the wastewater is ≥0.5 mg / L and the COD is ≥120 mg / L, the wastewater is circulated back to the electrochemical reactor for further treatment.

2. The processing method according to claim 1, characterized in that: In step A), in the UDMH wastewater, the concentration of UDMH is 10,000-50,000 mg / L, and the COD concentration is 20,000-100,000 mg / L.

3. The processing method according to claim 1, characterized in that: In step B), the absorbed dose of a single electron beam irradiation is 10 to 50 kGy.

4. The processing method according to claim 1, characterized in that: In step B), the filtered wastewater is directly subjected to electron beam irradiation treatment under the action of electrocatalysis to accumulate absorbed dose without adding chemical agents.

5. The processing method according to claim 4, characterized in that: The current density of the electrocatalysis is 800-1500 mA / cm 2 The electrocatalytic residence time is 2 to 12 hours.

6. The processing method according to claim 1, characterized in that: In step B), the parameters of the electron beam irradiation treatment include: The electron accelerator energy is 0.5-10.0 MeV, the beam current is 2-80 mA, the single irradiation dose is 10-50 kGy, and the water film thickness under the beam is 0.05-1.0 cm.

7. The processing method according to claim 1, characterized in that: In step C), the electrolyte includes NaCl or Na2SO4.

8. The processing method according to claim 1, characterized in that: In step C), electrolytes are added during the electrochemical reaction to ensure that the TDS concentration in the water is above 5000 mg / L.

9. The processing method according to claim 1, characterized in that: In step C), the temperature of the electrochemical reaction does not exceed 40°C.

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